Various optical multiplexing apparatuses and projectors for emitting highly bright light at high power have been proposed. For example, Patent Document 1 discloses an illuminator which has a few light source units. The illuminator has a fly-eye lens to which convergent beams emitted from the light source units enter at different incident angles. The illuminator uses the fly-eye lens to multiplex the beams.
Patent Document 2 discloses a display apparatus which projects highly bright light. The display apparatus has a few light source units. The beams from the light source units are collimated, and then enter one fly-eye lens. The incident beams to the fly-eye lens are parallel with each other. The display apparatus uses the fly-eye lens to multiplex the beams.
Patent Document 3 discloses an image display apparatus which has two light sources. The polarization planes of the beams emitted from the light sources are perpendicular to each other. The image display apparatus uses a polarizing prism to multiplex the beams.
Patent Document 4 discloses an illuminator which has a few laser sources for emitting collimated beams. The illuminator has a special prism configured to reduce optical axis intervals of the collimated beams. The illuminator uses an inclined surface of the prism to multiplex the beams.
According to the technologies disclosed in Patent Document 1, the beams multiplexed by the fly-eye lens become divergent light thereafter. Therefore, an increase in a quantity of the light source units increases the divergent angle. This means that the illuminator of Patent Document 1 needs a large optical system to process the multiplexed light.
According to the technologies disclosed in Patent Document 2, an increase in a quantity of the light source units means an increase in collimated beams, which are parallel with each other. Therefore, like the illuminator of Patent Document 1, the display apparatus of Patent Document 2 needs a large optical system to process the multiplexed light.
The image display apparatus of Patent Document 3 uses the polarization planes, which are perpendicular to each other, and the polarizing prism to multiplex the beams. Therefore, a quantity of the light source units, which is available according to the disclosed technologies in Patent Document 3, is limited to two. This means that the disclosed technologies in Patent Document 3 are not directed to increase a quantity of the light source units.
According to the technologies disclosed in Patent Document 4, an increase in a quantity of the light source units means an increase in collimated beams, which are parallel with each other, like the display apparatus of Patent Document 2. The illuminator of Patent Document 4 uses the special prism to reduce the optical axis intervals of the collimated beams, but still needs a large optical system to process the multiplexed light.
Patent Document 1: JP H5-045605 A
Patent Document 2: JP H10-293545 A
Patent Document 3: JP 2000-180795 A
Patent Document 4: JP 2003-31872 A